Field of the Invention
The present invention relates to the field of microbial production. In particular, it relates to a method of using a novel microorgarnism to reduce the precursor of ethyl carbamate in soy sauce.
Description of the Related Art
Ethyl carbamate (EC) widely exists in fermented products such as rice wine, wine, soy sauce and soybean paste. EC is classified as a class 2A carcinogen by the World Health Organization (WHO). It has been reported that EC could induce lung cancer, liver cancer, skin cancer and other cancers. It has aroused widespread concerns as to the food safety issue caused by EC in fermented products. However, there is no effective way to remove the EC in soy sauce. EC generated from precursors during soy sauce sterilization process is extremely hard to be degraded.
An effective way to remove EC in soy sauce is reducing the amount of EC precursors. Studies have shown that ethanol, citrulline and urea are the main precursors for producing EC in soy sauce. The amount of ethanol, citrulline and urea in soy sauce is 2.5%, 2.2 g/L and 57 mg/L, respectively. 80% of EC in soy sauce is made by reaction of ethanol and citrulline. Since ethanol is a primary flavoring compound in soy sauce, reducing citrulline accumulation in soy sauce is an effective way to decrease the amount of EC without affecting soy sauce flavor.
Tetragenococcus halophilus belongs to genus Lactobacillus, which is formerly classified as halophilic Pediococcus, and is now classified as a Tetragenococcus. It exists widely in salted products, such as Japanese soy sauce, salted anchovies and Indonesia soy sauce. Adding Tetragenococcus halophilus in the production of soy sauce can improve the flavor and quality of the soy sauce. It has no report that addition of Tetragenococcus halophilus can decrease the accumulation of EC in soy sauce. It is the goal of the present invention to provide a method of reducing the amount of EC precursors in soy sauce by use of a novel strain of Tetragenococcus halophilus. 